From what I have heard the words "repair & reasonable price" are incompatible in this field.
You could try taking your camera into a "good" photo dealer and asking them for an opinion. However, as you say you have changed the batteries, which I assume are new AA alkaline (not rechargeable) type, it seems the problem is not going to be easily resolved.
It is probably bite the bullet time, and a new camera is on the cards. Consider going for a higher pixel resolution than the 3.1 on the Nikon. I really did see the difference when I went from a 3Mpix Fuji to my current 5Mpix Canon.